The present invention relates to gas-shielded welding tip reconditioning apparatus, and particularly to improvements therein useful in robotic MIG welding operations. xe2x80x9cWeldingxe2x80x9d in the context of the present invention relates to the co-joining of two or more metal parts. The quality of the weld is affected by a number of factors, including the selection of any given welding technology, the competency of the operator, and of particular importance in the present context, the condition of the welding equipment. With regard to the condition of the equipment, the condition of the welding tip is often important. In the case of resistance welding equipment, for example, there are a variety of devices useful in connection with welding electrode maintenancexe2x80x94including surface reconditioning apparatus those disclosed in the following patents: U.S. Pat. No. 4,682,487; U.S. Pat. No. 4,856,949; U.S. Pat. No. 4,916,931; and U.S. Pat. No. 4,921,377.
Another well known welding technique is ARC weldingxe2x80x94which differs from resistance welding in that ARC welding electrodes are deliberately consumed during the welding process so that the electrode material becomes an integral component of the finished weld. As a result, the problem of electrode reconditioning that is associated with resistance welding equipment, is not a problem in ARC welding.
MIG (and acronym for xe2x80x9cmetal-inert-gasxe2x80x9d) arc welding is an arc welding technique in which a relatively fine wire electrode is fed continuously from a large spool mounted on by a variable speed drive whose speed is controlled to optimise arc length and burnoff rate. During the welding process, the electrical arc that extends between the electrode and the metal surfaces that are being welded, is shielded within a gas flow. Typically argon or other gases having suitable characteristics, or mixtures thereof are usedxe2x80x94with carbon dioxide often being the gas of commercial choice.
In gas shielded welding the wire electrode and the gas are generally channelled through a so-called xe2x80x9ctorchxe2x80x9d, which includes a central, electrically charged xe2x80x9ctipxe2x80x9d. The tip directs the wire electrode toward the weld site, and a concentrically arranged metal gas shield (that is electrically insulated from the tip), acts as a hood to direct and maintain a coaxial flow of the inert gas in surrounding relation about the wire. The quality of the weld is contingent on both consistent and continuous gas flow and arc patterning. Anything that interferes with the gas flow or redirects or otherwise militates against the desired electrical arc pattern, will diminish the quality of the weld.
MIG welding, when properly executed, permits high welding speeds, and necessitates less operator training than is required in the case of other welding techniques. In applications where one or the other or both of these benefits are sought, the weld quality is especially sensitive to those variations that are attributable to adverse gas flow or anything which could negatively influence the desired arc pattern.
Gas flow in MIG welding can be adversely effected as a consequence of molten metal deposition. This arises as a result of backsplash splatter on the respective mutually opposed surfaces of the tip and the hood, within the interior of the torch. Similarly, (since the dielectric strength of the gas flow is otherwise a constant), the accumulation of such backsplash splatter decreases the physical and hence xe2x80x9celectricalxe2x80x9d distance between the charged tip and the electrically insulated hood. If the distance decreases sufficiently, the voltage differential will exceed the dielectric strength of the intervening gas flow, and the arc will jump between the tip and the hood. This results in a diminished amount of electrical energy being delivered to the weld site and a concomitant compromise in weld quality.
In view of the foregoing, it is important that MIG welding torches be cleaned regularly, in order to avoid these two latter mentioned problems. A variety of devices are available for this purpose, and many if not most involve mechanical devices such as torch clamps and reaming tool drives, that can be exposed to and damaged by the debris that is dislodged from the torch. The present invention is intended to help remedy or at least reduce the incidence/severity of such damage.
The present invention relates generally to a MIG welding torch reconditioning apparatus including a pneumatic supply line; vent; and a mechanical transmission shaft. The pneumatic supply line supplies air to the vent which in turn then vents a directed debris-scattering air-flow against the mechanical transmission shaft proximal to exposed seals thereon. This arrangement is particularly advantageous as part of a combination in which the MIG welding torch reconditioning apparatus has a pneumatic supply line that is connected to supply a pneumatically driven mechanical means, and to vent xe2x80x9cspent-drivexe2x80x9d air that exits from the mechanical means, through vent means as described above.
In a more specific embodiment, a MIG welding torch reconditioning apparatus according to the present invention includes a pneumatic supply line for supplying pneumatic rotary drive means, as well as a drive vent means for venting the directed debris-scattering air-flow towards a mechanical transmission shaft proximal to seals thereon. Preferably, this transmission shaft is a rotary drive shaft that is arranged in driven relation to the pneumatic drive means. The transmission shaft is also connected, in turn, in driving relation to a reaming tool that is adapted to be aligned and inserted within a torches gas-shield and to be operable therein to remove at least some of any back-splash deposits laid down on interior surfaces of the gas-shield. In an especially preferred embodiment of this aspect of the invention, the transmission shaft is an extensible rotary drive shaft, adapted to be retractably extended past a seal to position the reaming tool within said gas shield.
In an alternative aspect of the present invention there is provided a MIG welding torch reconditioning apparatus which includes a pneumatic supply line for supplying pneumatic lift means and wherein lift vent means is included, for venting a directed debris-scattering air-flow towards a mechanical transmission shaft proximal to seals thereon. In a preferred form of this particular embodiment, the transmission shaft is an extensible shaft, adapted to be retractably extended past said seals to position a reaming tool within a gas shield. An especially advantageous embodiment of this aspect of the invention involves the transmission shaft being a rotary drive shaft arranged in driving relation with a reaming tool to be aligned and inserted within a torches gas-shield and to be operable therein to remove at least some of any back-splash deposits laid down on interior surfaces of said gas-shield.
In a general sense, the present invention relates to MIG welding torch reconditioning apparatus comprising: a pneumatic supply line; pneumatic lift means powered from said supply line, pneumatic rotary drive means powered from said supply line; a mechanical transmission shaft that is connected in rotary driven relation to paid drive means and is retractably extensible on operation of said lift means. In this type of embodiment, an exhaust vent supplied by one of: air directly from said supply line; exhausted air flow from said lift means; exhausted air from said rotary drive means; or a combination of any of the forgoing. This exhaust vent is operable to vent a directed debris-scattering air-flow from these various sources, towards a said transmission shaft proximal to seals thereon. In an especially preferred form this exhaust vent is supplied at least in part by exhausted air from the rotary drive means.
In another embodiment, there is generally provided a MIG torch reconditioning apparatus which comprises an in-line, direct-drive arrangement of a motor, a mechanical transmission shaft, and chuck for receiving a reaming tool. A pneumatic lift means is provided to lift the direct drive arrangement into reaming tool engagement, (wherein the tool is positioned within a torches gas shield and operable to remove at least some of any back-splash deposits laid down on interior surfaces of said gas shield). Preferable, embodiments of this aspect of the invention include a pneumatic motor as part of the direct drive means.
In a preferred form, the direct-drive arrangement is movably arranged as a piston within a channel in a housing, and the pneumatic lift means is operable to introduce a supply of air under pressure into the channel to move the piston arrangement there-along. In an exemplary embodiment of this aspect of the present invention the direct-drive arrangement includes a cradle for supporting said pneumatic motor within the channel. The cradle comprises surfaces that are adapted to cooperate with interior channel surfaces of the housing, to form a sliding air-tight seal there-between. Typically, these cradle surfaces will include sealing rings. In addition, it is preferable in embodiments where the channel is cylindrical, that the cradle be mounted in slidably positionable relation along an at least one guide rail that is arranged within the channel. The longitudinal axis of the guide rail is oriented parallel to the channels longitudinal axis, and the rail located in an axially offset relation from the direct drive arrangement. In this way, the guide rails serves to resist reactionary rotation of the cradle within the channel during the operation of the direct drive means.
In a particularly preferred embodiment, the apparatus according to the present invention further includes a pneumatic retractor means. This retractor is operable to retract the direct drive arrangement from out of reaming tool engagement within the torches gas shield, once the tool has removed at least some of any back-splash deposits that may have been laid down on interior surfaces of the gas shield.
A preferred embodiment of the present invention includes a cradle which comprises at least two, mutually spaced apart sealing surfaces. A space is defined there-between which is otherwise also bounded by adjacent cradle and channel surface portions. A pneumatic inlet is provide through the housing and opens up into that space. In addition, the cradle includes a pneumatic (conduit) passage communicating between the space and an air inlet into the pneumatic motor. In this arrangement, air that is supplied through the housing inlet is deliverable to the motor through the above mentioned xe2x80x9cspacexe2x80x9d and the xe2x80x9cpassagexe2x80x9d over a range of positions in which the inlet is in register between the spaced apart sealing surfaces. In this way, the motor can be powered over a range of its axial positioning, relative to the introduction and retraction of the reaming tool into and from a gas shield.
Moreover, it is also preferred that the cradle include a port for exhausting drive air from the motor. Such a port can comprise, for example, a telescoping snorkel adapted to channel drive air exhaust exteriorly of the housing.
In yet another embodiment of the present invention, there is generally provided a MIG welding torch reconditioning apparatus which comprises means adapted to hold a reaming tool to be aligned and inserted within a torches gas-shield. The reaming tool is itself adapted to be operable within the confines of the gas-shield to remove at least some of any back-splash deposits laid down on interior surfaces of said gas-shield.
When the apparatus is in use the motor-driven reaming tool is operable in intermittently driven relation. More specifically, when an incipient stall condition arises, (i.e. a condition in which the torque available from the motor is insufficient to properly rotate the reaming tool against loads occasioned by contact of the reaming tool against welding deposits within the gas-shield), then the apparatus responds by causing the motor to discontinue driving the reaming tool until sufficient motive force can be brought to impact through the reaming tool and in turn against the contacted deposits. This in turn, is intended to allow the apparatus to return to it normal reaming operation.
The advantages of this apparatus are particularly applicable to small pneumatic motors. Accordingly, in a contemplated embodiment of the present invention the torch reconditioning apparatus described above, might include a pneumatic motor and its drive would be suspended as contemplated above, by the specific means of a feed-back operated valve in a pneumatic supply line to the motor. This valve would be operative in response to feed-back signaling an incipient stall condition, to interrupt an air supply from driving the motor. It would then suddenly reconnect the air supply to provide sufficient motive force to impact through the reaming tool against the contacted deposits, to allow the apparatus to return to normal reaming operation.
Although this arrangement may provide some of the benefit associated with the present invention, there is every reason to believe that more efficacious results might be realized through the use of clutch means to selectively uncouple and re-couple the motor (whether pneumatic or otherwise) from driving relation with the reaming tool. The clutch would be thereby operable when the motor encounters an incipient stall condition, to responds by causing the motor to discontinue driving the reaming tool. Such discontinuity would persist until sufficient motive force can be brought upon re-engaging said clutch, to impact through the reaming tool and in turn against the contacted deposits.
A clutch within the present contemplation might, without limiting the generality of the explicit function, be mechanical, electrical, pneumatic or hydraulic in its operation.
Generally speaking, therefore, it is preferable for the purposes of the present invention that the MIG welding torch reconditioning apparatus comprise torch reconditioning means adapted to hold a reaming tool to be aligned and inserted within a torches gas-shield; and, to be operable therein to remove at least some of any back-splash deposits laid down on interior surfaces of said gas-shield, and wherein said torch reconditioning means includes an intermittent drive coupling arranged intermediate between a motor and said reaming tool, and operable there between to uncouple a reaming tool transmission side of said coupling from a motor-powered drive side of said coupling when, in operation, the torque available from the motor is insufficient to properly rotate the reaming tool against loads occasioned by contact of the reaming tool against welding deposits within the gas-shield, whereupon the motor rotates the drive side of the coupling under unloaded-motor conditions until the drive coupling re-couples through complementary mating surfaces thereof to thereby transmit the resulting impact force through the reaming tool and against and contacted deposits.
In a particularly preferred form of the present invention, there is provided a MIG welding torch reconditioning apparatus comprising, torch reconditioning means adapted to hold a reaming tool to be aligned and inserted within a torches gas-shield; and, to be operable therein to remove at least some of any back-splash deposits laid down on interior surfaces of said gas-shield, and wherein said torch reconditioning means includes a mechanical, impact-clutch intermittent drive coupling arranged intermediate between a motor and said reaming tool, and operable there between to uncouple a reaming tool transmission side of said coupling from a motor-powered drive side of said coupling when, in operation, the torque available from the motor is insufficient to properly rotate the reaming tool against loads occasioned by contact of the reaming tool against welding deposits within the gas-shield, whereupon the motor rotates the drive side of the coupling under unloaded-motor conditions until the drive coupling re-couples through complementary mating surfaces thereof to thereby transmit the resulting impact force through the reaming tool and against and contacted deposits.
Again, this apparatus is particularly useful in combination with a pneumatically driven motor. Particular versatility can be realized when the coupling is reversibly operable and the motor is a reversible pneumatically driven motor.
In an especially preferred form, the present invention comprises a MIG welding torch reconditioning apparatus comprising, torch reconditioning means that is adapted to hold a reaming tool to be aligned and inserted within a torches gas-shield. When so held, the reaming tool is operable to remove at least some of any back-splash deposits laid down on interior surfaces of said gas-shield.
In addition, the torch reconditioning means includes an impact-clutch intermittent drive coupling arranged intermediate between a motor and the reaming tool. The drive coupling is operable in two modes.
In a first mode, it operates to uncouple a reaming tool transmission side of said coupling from a motor-powered drive side of said coupling. This it accomplishes through disengagement of complementary hammer and reception block surfaces of the coupling which it does under predetermined high motor-load conditions.
In a second mode, the drive coupling operates to re-couple the drive and transmission sides of the coupling, which it does by impacting the hammer and reception block surfaces against one another.
Thus, when this latter embodiment is in operation, and the torque available from the motor is insufficient to properly rotate the reaming tool against loads occasioned by contact of the reaming tool against welding deposits within the gas-shield, then the drive coupling uncouples the tool from the motor. Once uncoupled from the reaming tool loading, the motor rotates the drive side of the coupling freely under unloaded-motor conditions. This forces the hammer and reception block surfaces to impact against one another and to thereby transmit the resulting impact force through the reaming tool and against the contacted deposits and greatly increases the instantaneous forces that are available to dislodge that material.
In still another embodiment of the present invention, a clamp is provided for engaging a cylindrical body between a pair of generally orthogonally-offset faces of a xe2x80x9cVxe2x80x9d-block and respective gripping surfaces on gripping surface members of a pair of opposed jaws. The jaws are arranged on respective jaw pivots and also include respective lever arms which extend beyond the pivots. Each such lever arm supports respective cam followers in spaced apart relation from their respective jaw pivots. The clamp also includes movable cam surfaces which are adapted to act on the cam followers in such a way as to rotate the lever arms and associated jaws about their pivots. This translates in turn, into movement of the gripping surfaces in and out of a three-way engagement of the cylindrical body between said surfaces and the xe2x80x9cVxe2x80x9d-block (or more specifically, the above mentioned xe2x80x9cfacesxe2x80x9d thereof.
In a preferred form of the clamp, each of the orthogonally-offset faces are arranged in generally parallel, mutually-opposed relation to a corresponding gripping surface on a gripping surface member. The xe2x80x9cVxe2x80x9d-block in this clamp, is mounted on a xe2x80x9cVxe2x80x9d-block pivot and is rotatable about same to permit the cylindrical body to be engaged in a self-centering relation between the xe2x80x9cfacesxe2x80x9d and the xe2x80x9csurfacesxe2x80x9d of the jaws and the xe2x80x9cVxe2x80x9d-block, respectively.
Preferably, the cam surfaces are side walls of a milled track arranged in a slide plate which is selectively movable between positions corresponding to the gripping surfaces being, respectively, in and out of the three-way clamp engagement of the cylindrical body.
In an additionally preferred feature of the invention, the cam surfaces are comprised of a primary portion that is configured to direct the cam followers and to translate the motion thereof through the lever arms, to move the jaws rapidly towards engagement with a lower mechanical advantage. A secondary portion of the cam surfaces are configured to direct the cam followers and thereby translate the motion thereof through the lever means, to move the jaws more slowly into engaged relation with the cylindrical body, with greater mechanical advantage.
The plate is preferably selectively driven by a pneumatic piston.
The clamp according to the present invention is desirably arranged such that the plate, the lever arms, and the cam followers are enclosed within a housing, while the xe2x80x9cVxe2x80x9d-block and the gripping surface members arranged externally thereof. A central resilient cylindrical seal is arranged generally tangentially against the jaws, between and proximal to the jaw pivots, to thereby reduce ingress of debris into the housing. Respective ones of outboard cylindrical seals are arranged adjacent the pivots and generally tangentially between corresponding ones of the jaws, and adjacent portions of the housing, to thereby reduce ingress of debris into the housing.